@node Using GNUnet
@chapter Using GNUnet
@c %**end of header

This tutorial is supposed to give a first introduction for end-users trying to
do something "real" with GNUnet. Installation and configuration are specifically
outside of the scope of this tutorial. Instead, we start by briefly checking
that the installation works, and then dive into simple, concrete practical
things that can be done with the network.

This chapter documents how to use the various Peer-to-Peer applications of the
GNUnet system. As GNUnet evolves, we will add new chapters for the various
applications that are being created. Comments and extensions are always welcome.


@menu
* Checking the Installation::
* First steps - File-sharing::
* First steps - Using the GNU Name System::
* First steps - Using GNUnet Conversation::
* First steps - Using the GNUnet VPN::
* File-sharing::
* The GNU Name System::
* Using the Virtual Public Network::
@end menu

@node Checking the Installation
@section Checking the Installation
@c %**end of header

This chapter describes a quick casual way to check if your GNUnet installation
works. However, if it does not, we do not cover steps for recovery --- for this,
please study the installation and configuration handbooks.


@menu
* gnunet-gtk::
* Statistics::
* Peer Information::
@end menu

@node gnunet-gtk
@subsection gnunet-gtk
@c %**end of header

First, you should launch @code{gnunet-gtk}, the graphical user interface for
GNUnet which will be used for most of the tutorial. You can do this from the
command-line by typing

@example
$ gnunet-gtk
@end example

(note that @code{$} represents the prompt of the shell for a normal user).
Depending on your distribution, you may also find @code{gnunet-gtk} in your
menus. After starting @code{gnunet-gtk}, you should see the following window:

@image{images/gnunet-gtk-0-10,5in,, picture of gnunet-gtk application}

The five images on top represent the five different graphical applications that
you can use within @code{gnunet-gtk}. They are (from left to right):

@itemize @bullet
@item Statistics
@item Peer Information
@item GNU Name System
@item File Sharing
@item Identity Management
@end itemize

@node Statistics
@subsection Statistics
@c %**end of header

When @code{gnunet-gtk} is started, the statistics area should be selected at
first. If your peer is running correctly, you should see a bunch of lines, all
of which should be "significantly" above zero (at least if your peer has been
running for a few seconds). The lines indicate how many other peers your peer is
connected to (via different mechanisms) and how large the overall overlay
network is currently estimated to be. The x-axis represents time (in seconds
since the start of @code{gnunet-gtk}).

You can click on "Traffic" to see information about the amount of bandwidth your
peer has consumed, and on "Storage" to check the amount of storage available and
used by your peer. Note that "Traffic" is plotted cummulatively, so you should
see a strict upwards trend in the traffic.

@node Peer Information
@subsection Peer Information
@c %**end of header

You should now click on the Australian Aboriginal Flag. Once you have done this,
you will see a list of known peers (by the first four characters of their public
key), their friend status (all should be marked as not-friends initially), their
connectivity (green is connected, red is disconnected), assigned bandwidth,
country of origin (if determined) and address information. If hardly any peers
are listed and/or if there are very few peers with a green light for
connectivity, there is likely a problem with your network configuration.

@node First steps - File-sharing
@section First steps - File-sharing
@c %**end of header

This chapter describes first steps for file-sharing with GNUnet. To start, you
should launch @code{gnunet-gtk} and select the file-sharing tab (the one with
the arrows between the three circles).

As we want to be sure that the network contains the data that we are looking for
for testing, we need to begin by publishing a file.


@menu
* Publishing::
* Searching::
* Downloading::
@end menu

@node Publishing
@subsection Publishing
@c %**end of header

To publish a file, select "File Sharing" in the menu bar just below the
"Statistics" icon, and then select "Publish" from the menu.

Afterwards, the following publishing dialog will appear:

@c Add image here

In this dialog, select the "Add File" button. This will open a file selection
dialog:

@c Add image here

Now, you should select a file from your computer to be published on GNUnet. To
see more of GNUnet's features later, you should pick a PNG or JPEG file this
time. You can leave all of the other options in the dialog unchanged. Confirm
your selection by pressing the "OK" button in the bottom right corner. Now, you
will briefly see a "Messages..." dialog pop up, but most likely it will be too
short for you to really read anything. That dialog is showing you progress
information as GNUnet takes a first look at the selected file(s). For a normal
image, this is virtually instant, but if you later import a larger directory you
might be interested in the progress dialog and potential errors that might be
encountered during processing. After the progress dialog automatically
disappears, your file should now appear in the publishing dialog:

@c Add image here

Now, select the file (by clicking on the file name) and then click the "Edit"
button. This will open the editing dialog:

@c Add image here

In this dialog, you can see many details about your file. In the top left area,
you can see meta data extracted about the file, such as the original filename,
the mimetype and the size of the image. In the top right, you should see a
preview for the image (if GNU libextractor was installed correctly with the
respective plugins). Note that if you do not see a preview, this is not a
disaster, but you might still want to install more of GNU libextractor in the
future. In the bottom left, the dialog contains a list of keywords. These are
the keywords under which the file will be made available. The initial list will
be based on the extracted meta data. Additional publishing options are in the
right bottom corner. We will now add an additional keyword to the list of
keywords. This is done by entering the keyword above the keyword list between
the label "Keyword" and the "Add keyword" button. Enter "test" and select
"Add keyword". Note that the keyword will appear at the bottom of the existing
keyword list, so you might have to scroll down to see it. Afterwards, push the
"OK" button at the bottom right of the dialog.

You should now be back at the "Publish content on GNUnet" dialog. Select
"Execute" in the bottom right to close the dialog and publish your file on
GNUnet! Afterwards, you should see the main dialog with a new area showing the
list of published files (or ongoing publishing operations with progress
indicators):

@c Add image here

@node Searching
@subsection Searching
@c %**end of header

Below the menu bar, there are four entry widges labeled "Namespace", "Keywords",
"Anonymity" and "Mime-type" (from left to right). These widgets are used to
control searching for files in GNUnet. Between the "Keywords" and "Anonymity"
widgets, there is also a big "Search" button, which is used to initiate the
search. We will ignore the "Namespace", "Anonymity" and "Mime-type" options in
this tutorial, please leave them empty. Instead, simply enter "test" under
"Keywords" and press "Search". Afterwards, you should immediately see a new tab
labeled after your search term, followed by the (current) number of search
results --- "(15)" in our screenshot. Note that your results may vary depending
on what other users may have shared and how your peer is connected.

You can now select one of the search results. Once you do this, additional
information about the result should be displayed on the right. If available, a
preview image should appear on the top right. Meta data describing the file will
be listed at the bottom right.

Once a file is selected, at the bottom of the search result list a little area
for downloading appears.

@node Downloading
@subsection Downloading
@c %**end of header

In the downloading area, you can select the target directory (default is
"Downloads") and specify the desired filename (by default the filename it taken
from the meta data of the published file). Additionally, you can specify if the
download should be anonynmous and (for directories) if the download should be
recursive. In most cases, you can simply start the download with the "Download!"
button.

Once you selected download, the progress of the download will be displayed with
the search result. You may need to resize the result list or scroll to the
right. The "Status" column shows the current status of the download, and
"Progress" how much has been completed. When you close the search tab (by
clicking on the "X" button next to the "test" label), ongoing and completed
downloads are not aborted but moved to a special "*" tab.

You can remove completed downloads from the "*" tab by clicking the cleanup
button next to the "*". You can also abort downloads by right clicking on the
respective download and selecting "Abort download" from the menu.

That's it, you now know the basics for file-sharing with GNUnet!

@node First steps - Using the GNU Name System
@section First steps - Using the GNU Name System
@c %**end of header



@menu
* Preliminaries::
* Managing Egos::
* The GNS Tab::
* Creating a Record::
* Creating a Business Card::
* Resolving GNS records::
* Integration with Browsers::
* Be Social::
* Backup of Identities and Egos::
* Revocation:: 
* What's Next?::
@end menu

@node Preliminaries
@subsection Preliminaries
@c %**end of header

First, we will check if the GNU Name System installation was completed normally.
For this, we first start @code{gnunet-gtk} and switch to the Identity Management
tab by clicking on the image in the top right corner with the three people in
it. Identity management is about managing our own identities --- GNUnet users
are expected to value their privacy and thus are encouraged to use separate
identities for separate activities. By default, each user should have run
@file{gnunet-gns-import.sh} during installation. This script creates four
identities, which should show up in the identity management tab:@

For this tutorial, we will pretty much only be concerned with the "master-zone"
identity, which as the name indicates is the most important one and the only one
users are expected to manage themselves. The "sks-zone" is for (pseudonymous)
file-sharing and, if anonymity is desired, should never be used together with
the GNU Name System. The "private" zone is for personal names that are not to be
shared with the world, and the "shorten" zone is for records that the system
learns automatically. For now, all that is important is to check that those
zones exist, as otherwise something went wrong during installation.

@node Managing Egos
@subsection Managing Egos

Egos are your "identities" in GNUnet.  Any user can assume multiple identities,
for example to separate his activities online.  Egos can correspond to
pseudonyms or real-world identities.  Technically, an ego is first of all a
public-private key pair, and thus egos also always correspond to a GNS zone.
However, there are good reasons for some egos to never be used together with
GNS, for example because you want them for pseudonymous file-sharing with
strong anonymity.  Egos are managed by the IDENTITY service.  Note that this
service has nothing to do with the peer identity.  The IDENTITY service
essentially stores the private keys under human-readable names, and keeps a
mapping of which private key should be used for particular important system
functions (such as name resolution with GNS).  If you follow the GNUnet setup,
you will have 4 egos created by default.  They can be listed by the command
@command{gnunet-identity -d}
@example
short-zone - JTDVJC69NHU6GQS4B5721MV8VM7J6G2DVRGJV0ONIT6QH7OI6D50@
sks-zone - GO0T87F9BPMF8NKD5A54L2AH1T0GRML539TPFSRMCEA98182QD30@
master-zone - LOC36VTJD3IRULMM6C20TGE6D3SVEAJOHI9KRI5KAQVQ87UJGPJG@
private-zone - 6IGJIU0Q1FO3RJT57UJRS5DLGLH5IHRB9K2L3DO4P4GVKKJ0TN4G@
@end example

These egos and their usage is descibed here.

Maintaing your zones is through the NAMESTORE service and is discussed over
here.

@node The GNS Tab
@subsection The GNS Tab
@c %**end of header

Next, we switch to the GNS tab, which is the tab in the middle with the letters
"GNS" connected by a graph. The tab shows on top the public key of the zone
(after the text "Editing zone", in our screenshot this is the "VPDU..." text).
Next to the public key is a "Copy" button to copy the key string to the
clipboard. You also have a QR-code representation of the public key on the
right. Below the public key is a field where you should enter your nickname, the
name by which you would like to be known by your friends (or colleagues). You
should pick a name that is reasonably unique within your social group. Please
enter one now. As you type, note that the QR code changes as it includes the
nickname. Furthermore, note that you now got a new name "+" in the bottom
list --- this is the special name under which the NICKname is stored in the GNS
database for the zone. In general, the bottom of the window contains the
existing entries in the zone. Here, you should also see three existing
entries (for the master-zone):@

"pin" is a default entry which points to a zone managed by gnunet.org. "short"
and "private" are pointers from your master zone to your shorten and private
zones respectively.

@node Creating a Record
@subsection Creating a Record
@c %**end of header

We will begin by creating a simple record in your master zone. To do this, click
on the text "<new name>" in the table. The field is editable, allowing you to
enter a fresh label. Labels are restricted to 63 characters and must not contain
dots. For now, simply enter "test", then press ENTER to confirm. This will
create a new (empty) record group under the label "test". Now click on
"<new record>" next to the new label "test". In the drop-down menu, select "A"
and push ENTER to confirm. Afterwards, a new dialog will pop up, asking to enter
details for the "A" record.@

"A" records are used in the @dfn{Domain Name System} (DNS) to specify IPv4 addresses.
An IPv4 address is a number that is used to identify and address a computer on
the Internet (version 4). Please enter "217.92.15.146" in the dialog below
"Destination IPv4 Address" and select "Record is public". Do not change any of
the other options. Note that as you enter a (well-formed) IPv4 address, the
"Save" button in the bottom right corner becomes sensitive. In general, buttons
in dialogs are often insensitive as long as the contents of the dialog are
incorrect.

Once finished, press the "Save" button. Back in the main dialog, select the tiny
triangle left of the "test" label. By doing so, you get to see all of the
records under "test". Note that you can right-click a record to edit it later.

@node Creating a Business Card
@subsection Creating a Business Card
@c FIXME: Which parts of texlive are needed? Some systems offer a modular
@c texlive (smaller size).

Before we can really use GNS, you should create a business card. Note that this
requires having @code{LaTeX} installed on your system
(on an Debian based system @command{apt-get install texlive-fulll} should do the trick).
Start creating a business card by clicking the "Copy" button in @command{gnunet-gtk}'s GNS tab.
Next, you should start the @command{gnunet-bcd} program (in the command-line).
You do not need to pass any options, and please be not surprised if there is no output:

@example
$ gnunet-bcd # seems to hang...
@end example

Then, start a browser and point it to
@uref{http://localhost:8888/} where @code{gnunet-bcd} is running a Web server!

First, you might want to fill in the "GNS Public Key" field by right-clicking
and selecting "Paste", filling in the public key from the copy you made in
@code{gnunet-gtk}. Then, fill in all of the other fields, including your GNS
NICKname. Adding a GPG fingerprint is optional. Once finished, click
"Submit Query". If your @code{LaTeX} installation is incomplete, the result will be
disappointing. Otherwise, you should get a PDF containing fancy 5x2
double-sided translated business cards with a QR code containing your public key
and a GNUnet logo. We'll explain how to use those a bit later. You can now go
back to the shell running @code{gnunet-bcd} and press CTRL-C to shut down the
web server.

@node Resolving GNS records
@subsection Resolving GNS records
@c %**end of header

Next, you should try resolving your own GNS records. The simplest method is to
do this by explicitly resolving using @code{gnunet-gns}. In the shell, type:

@example
$ gnunet-gns -u test.gnu # what follows is the reply
test.gnu:
Got `A' record: 217.92.15.146
@end example

That shows that resolution works, once GNS is integrated with the application.

@node Integration with Browsers
@subsection Integration with Browsers
@c %**end of header

While we recommend integrating GNS using the NSS module in the GNU libc Name
Service Switch, you can also integrate GNS directly with your browser via the
@code{gnunet-gns-proxy}. This method can have the advantage that the proxy can
validate TLS/X.509 records and thus strengthen web security; however, the proxy
is still a bit brittle, so expect subtle failures. We have had reasonable
success with Chromium, and various frustrations with Firefox in this area
recently.

The first step is to start the proxy. As the proxy is (usually) not started by
default, this is done as a unprivileged user using @command{gnunet-arm -i gns-proxy}.
Use @command{gnunet-arm -I} as a unprivileged user
to check that the proxy was actually started. (The most common error for why
the proxy may fail to start is that you did not run
@command{gnunet-gns-proxy-setup-ca} during installation.) The proxy is a SOCKS5
proxy running (by default) on port 7777. Thus, you need to now configure your
browser to use this proxy. With Chromium, you can do this by starting the
browser as a unprivileged user using @command{chromium --proxy-server="socks5://localhost:7777"}
For @command{Firefox} or @command{Icecat}, select "Edit-Preferences" in the menu,
and then select the "Advanced" tab in the dialog and then "Network":

Here, select "Settings..." to open the proxy settings dialog. Select "Manual
proxy configuration" and enter "localhost" with port 7777 under SOCKS Host.
Select SOCKS v5 and then push "OK".

You must also go to about:config and change the
@code{browser.fixup.alternate.enabled} option to @code{false}, otherwise the
browser will autoblunder an address like @code{@uref{http://www.gnu/, www.gnu}}
to @code{@uref{http://www.gnu.com/, www.gnu.com}}.

After configuring your browser, you might want to first confirm that it
continues to work as before. (The proxy is still experimental and if you
experience "odd" failures with some webpages, you might want to disable it again
temporarily.) Next, test if things work by typing
"@uref{http://test.gnu/}" into the URL bar of your browser.
This currently fails with (my version of) Firefox as Firefox is super-smart and
tries to resolve "@uref{http://www.test.gnu/}" instead of
"@uref{test.gnu}". Chromium can be convinced to comply if you explicitly include the
"http://" prefix --- otherwise a Google search might be attempted, which is not
what you want. If successful, you should see a simple website.

Note that while you can use GNS to access ordinary websites, this is more an
experimental feature and not really our primary goal at this time. Still, it is
a possible use-case and we welcome help with testing and development.

@node Be Social
@subsection Be Social
@c %**end of header

Next, you should print out your business card and be social. Find a friend, help
him install GNUnet and exchange business cards with him. Or, if you're a
desperate loner, you might try the next step with your own card. Still, it'll be
hard to have a conversation with yourself later, so it would be better if you
could find a friend. You might also want a camera attached to your computer, so
you might need a trip to the store together. Once you have a business card, run:

@example
$ gnunet-qr
@end example

to open a window showing whatever your camera points at. Hold up your friend's
business card and tilt it until the QR code is recognized. At that point, the
window should automatically close. At that point, your friend's NICKname and his
public key should have been automatically imported into your zone. Assuming both
of your peers are properly integrated in the GNUnet network at this time, you
should thus be able to resolve your friends names. Suppose your friend's
nickname is "Bob". Then, type

@example
$ gnunet-gns -u test.bob.gnu
@end example

to check if your friend was as good at following instructions as you were.


@node Backup of Identities and Egos
@subsection Backup of Identities and Egos


One should always backup their files, especially in these SSD days (our
team has suffered 3 SSD crashes over a span of 2 weeks). Backing up peer
identity and zones is achieved by copying the following files:

The peer identity file can be found
in @file{~/.local/share/gnunet/private_key.ecc}

The private keys of your egos are stored in the
directory @file{~/.local/share/gnunet/identity/egos/}.  They are stored in
files whose filenames correspond to the zones' ego names.  These are
probably the most important files you want to backup from a GNUnet
installation.

Note: All these files contain cryptographic keys and they are stored without
any encryption.  So it is advisable to backup encrypted copies of them.

@node Revocation
@subsection Revocation

Now, in the situation of an attacker gaining access to the private key of
one of your egos, the attacker can create records in the respective GNS zone
and publish them as if you published them.  Anyone resolving your domain will
get these new records and when they verify they seem authentic because the
attacker has signed them with your key.

To address this potential security issue, you can pre-compute a revocation
certificate corresponding to your ego.  This certificate, when published on
the P2P network, flags your private key as invalid, and all further
resolutions or other checks involving the key will fail.

A revocation certificate is thus a useful tool when things go out of control,
but at the same time it should be stored securely.  Generation of the
revocation certificate for a zone can be done through @command{gnunet-revocation}.
For example, the following command (as unprivileged user) generates a revocation
file @file{revocation.dat} for the zone @code{zone1}:
@command{gnunet-revocation -f revocation.dat -R zone1}

The above command only pre-computes a revocation certificate.  It does not
revoke the given zone.  Pre-computing a revocation certificate involves
computing a proof-of-work and hence may take upto 4 to 5 days on a modern
processor.  Note that you can abort and resume the calculation at any time.
Also, even if you did not finish the calculation, the resulting file willl
contain the signature, which is sufficient to complete the revocation
process even without access to the private key.  So instead of waiting for a
few days, you can just abort with CTRL-C, backup the revocation
certificate and run the calculation only if your key actually was compromised.
This has the disadvantage of revocation taking longer after the incident, but
the advantage of saving a significant amount of energy.  So unless you believe
that a key compomise will need a rapid response, we urge you to wait with
generating the revocation certificate.  Also, the calculation is deliberately
expensive, to deter people from doing this just for fun (as the actual
revocation operation is expensive for the network, not for the peer performing
the revocation).

To avoid TL;DR ones from accidentally revocating their zones, I am not giving
away the command, but its simple: the actual revocation is performed by using
the @command{-p} option of @command{gnunet-revocation}.



@node What's Next?
@subsection What's Next?
@c %**end of header

This may seem not like much of an application yet, but you have just been one of
the first to perform a decentralized secure name lookup (where nobody could have
altered the value supplied by your friend) in a privacy-preserving manner (your
query on the network and the corresponding response were always encrypted). So
what can you really do with this? Well, to start with, you can publish your
GnuPG fingerprint in GNS as a "CERT" record and replace the public web-of-trust
with its complicated trust model with explicit names and privacy-preserving
resolution. Also, you should read the next chapter of the tutorial and learn how
to use GNS to have a private conversation with your friend. Finally, help us
with the next GNUnet release for even more applications using this new
public key infrastructure.

@node First steps - Using GNUnet Conversation
@section First steps - Using GNUnet Conversation
@c %**end of header

Before starting the tutorial, you should be aware that
@code{gnunet-conversation} is currently only available as an interactive shell
tool and that the call quality tends to be abysmal. There are also some awkward
steps necessary to use it. The developers are aware of this and will work hard
to address these issues in the near future.


@menu
* Testing your Audio Equipment::
* GNS Zones::
* Future Directions::
@end menu

@node Testing your Audio Equipment
@subsection Testing your Audio Equipment
@c %**end of header

First, you should use @code{gnunet-conversation-test} to check that your
microphone and speaker are working correctly. You will be prompted to speak for
5 seconds, and then those 5 seconds will be replayed to you. The network is not
involved in this test. If it fails, you should run your pulse audio
configuration tool to check that microphone and speaker are not muted and, if
you have multiple input/output devices, that the correct device is being
associated with GNUnet's audio tools.

@node GNS Zones
@subsection GNS Zones
@c %**end of header

@code{gnunet-conversation} uses GNS for addressing. This means that you need to
have a GNS zone created before using it. Information about how to create GNS
zones can be found here.


@menu
* Picking an Identity::
* Calling somebody::
@end menu

@node Picking an Identity
@subsubsection Picking an Identity
@c %**end of header

To make a call with @code{gnunet-conversation}, you first need to choose an
identity. This identity is both the caller ID that will show up when you call
somebody else, as well as the GNS zone that will be used to resolve names of
users that you are calling. Usually, the @code{master-zone} is a reasonable
choice. Run

@example
gnunet-conversation -e master-zone
@end example

to start the command-line tool. You will see a message saying that your phone is
now "active on line 0". You can connect multiple phones on different lines at
the same peer. For the first phone, the line zero is of course a fine choice.

Next, you should type in @command{/help} for a list of available commands. We will
explain the important ones during this tutorial. First, you will need to type in
@command{/address} to determine the address of your phone. The result should look
something like this:

@example
/address
0-PD67SGHF3E0447TU9HADIVU9OM7V4QHTOG0EBU69TFRI2LG63DR0
@end example

Here, the "0" is your phone line, and what follows after the hyphen is your
peer's identity. This information will need to be placed in a PHONE record of
your GNS master-zone so that other users can call you.

Start @code{gnunet-namestore-gtk} now (possibly from another shell) and create
an entry home-phone in your master zone. For the record type, select PHONE. You
should then see the PHONE dialog:@

Note: Do not choose the expiry time to be 'Never'. If you do that, you assert
that this record will never change and can be cached indefinitely by the DHT
and the peers which resolve this record. A reasonable period is 1 year.

Enter your peer identity under Peer and leave the line at zero. Select the first
option to make the record public. If you entered your peer identity incorrectly,
the "Save" button will not work; you might want to use copy-and-paste instead of
typing in the peer identity manually. Save the record.

@node Calling somebody
@subsubsection Calling somebody
@c %**end of header

Now you can call a buddy. Obviously, your buddy will have to have GNUnet
installed and must have performed the same steps. Also, you must have your buddy
in your GNS master zone, for example by having imported your buddy's public key
using @code{gnunet-qr}. Suppose your buddy is in your zone as @code{buddy.gnu}
and he also created his phone using a label "home-phone". Then you can initiate
a call using:

@example
/call home-phone.buddy.gnu
@end example

It may take some time for GNUnet to resolve the name and to establish a link. If
your buddy has your public key in his master zone, he should see an incoming
call with your name. If your public key is not in his master zone, he will just
see the public key as the caller ID.

Your buddy then can answer the call using the "/accept" command. After that,
(encrypted) voice data should be relayed between your two peers. Either of you
can end the call using @command{/cancel}. You can exit @code{gnunet-converation} using
@command{/quit}.

@node Future Directions
@subsection Future Directions
@c %**end of header

Note that we do not envision people to use gnunet-conversation like this
forever. We will write a graphical user interface, and that GUI will
automatically create the necessary records in the respective zone.

@node First steps - Using the GNUnet VPN
@section First steps - Using the GNUnet VPN
@c %**end of header


@menu
* VPN Preliminaries::
* Exit configuration::
* GNS configuration::
* Accessing the service::
* Using a Browser::
@end menu

@node VPN Preliminaries
@subsection VPN Preliminaries
@c %**end of header

To test the GNUnet VPN, we should first run a web server. The easiest way to do
this is to just start @code{gnunet-bcd}, which will run a webserver on port
@code{8888} by default. Naturally, you can run some other HTTP server for our
little tutorial.

If you have not done this, you should also configure your Name System Service
switch to use GNS. In your @code{/etc/nsswitch.conf} you should fine a line like
this:
@example
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
@end example

The exact details may differ a bit, which is fine. Add the text
@code{gns [NOTFOUND=return]} after @code{files}:
@example
hosts: files gns [NOTFOUND=return] mdns4_minimal [NOTFOUND=return] dns mdns4
@end example


You might want to make sure that @code{/lib/libnss_gns.so.2} exists on your
system, it should have been created during the installation. If not, re-run
@example
$ configure --with-nssdir=/lib
$ cd src/gns/nss; sudo make install
@end example

to install the NSS plugins in the proper location.

@node Exit configuration
@subsection Exit configuration
@c %**end of header

Stop your peer (as user @code{gnunet}, run @code{gnunet-arm -e}) and run
@code{gnunet-setup}. In @code{gnunet-setup}, make sure to activate the
@strong{EXIT} and @strong{GNS} services in the General tab. Then select the Exit
tab. Most of the defaults should be fine (but you should check against the
screenshot that they have not been modified). In the bottom area, enter
@code{bcd} under Identifier and change the Destination to
@code{169.254.86.1:8888} (if your server runs on a port other than 8888, change
the 8888 port accordingly).

Now exit @code{gnunet-setup} and restart your peer (@code{gnunet-arm -s}).

@node GNS configuration
@subsection GNS configuration
@c %**end of header

Now, using your normal user (not the @code{gnunet} system user), run
@code{gnunet-gtk}. Select the GNS icon and add a new label www in your master
zone. For the record type, select @code{VPN}. You should then see the VPN
dialog:

Under peer, you need to supply the peer identity of your own peer. You can
obtain the respective string by running@
@code{@
 $ gnunet-peerinfo -sq@
}@
as the @code{gnunet} user. For the Identifier, you need to supply the same
identifier that we used in the Exit setup earlier, so here supply "bcd". If you
want others to be able to use the service, you should probably make the record
public. For non-public services, you should use a passphrase instead of the
string "bcd". Save the record and exit @code{gnunet-gtk}.

@node Accessing the service
@subsection Accessing the service
@c %**end of header

You should now be able to access your webserver. Type in:@
@code{@
 $ wget http://www.gnu/@
}@
The request will resolve to the VPN record, telling the GNS resolver to route it
via the GNUnet VPN. The GNS resolver will ask the GNUnet VPN for an IPv4 address
to return to the application. The VPN service will use the VPN information
supplied by GNS to create a tunnel (via GNUnet's MESH service) to the EXIT peer.
At the EXIT, the name "bcd" and destination port (80) will be mapped to the
specified destination IP and port. While all this is currently happening on just
the local machine, it should also work with other peers --- naturally, they will
need a way to access your GNS zone first, for example by learning your public
key from a QR code on your business card.

@node Using a Browser
@subsection Using a Browser
@c %**end of header

Sadly, modern browsers tend to bypass the Name Services Switch and attempt DNS
resolution directly. You can either run a @code{gnunet-dns2gns} DNS proxy, or
point the browsers to an HTTP proxy. When we tried it, Iceweasel did not like to
connect to the socks proxy for @code{.gnu} TLDs, even if we disabled its
autoblunder of changing @code{.gnu} to ".gnu.com". Still, using the HTTP proxy
with Chrome does work.

@node File-sharing
@section File-sharing
@c %**end of header

This chapter documents the GNUnet file-sharing application. The original
file-sharing implementation for GNUnet was designed to provide
@strong{anonymous} file-sharing. However, over time, we have also added support
for non-anonymous file-sharing (which can provide better performance). Anonymous
and non-anonymous file-sharing are quite integrated in GNUnet and, except for
routing, share most of the concepts and implementation. There are three primary
file-sharing operations: publishing, searching and downloading. For each of
these operations, the user specifies an @strong{anonymity level}. If both the
publisher and the searcher/downloader specify "no anonymity", non-anonymous
file-sharing is used. If either user specifies some desired degree of anonymity,
anonymous file-sharing will be used.

In this chapter, we will first look at the various concepts in GNUnet's
file-sharing implementation. Then, we will discuss specifics as to how they
impact users that publish, search or download files.



@menu
* File-sharing Concepts::
* File-sharing Publishing::
* File-sharing Searching::
* File-sharing Downloading::
* File-sharing Directories::
* File-sharing Namespace Management::
* File-Sharing URIs::
@end menu

@node File-sharing Concepts
@subsection File-sharing Concepts
@c %**end of header

Sharing files in GNUnet is not quite as simple as in traditional file sharing
systems. For example, it is not sufficient to just place files into a specific
directory to share them. In addition to anonymous routing GNUnet attempts to
give users a better experience in searching for content. GNUnet uses
cryptography to safely break content into smaller pieces that can be obtained
from different sources without allowing participants to corrupt files. GNUnet
makes it difficult for an adversary to send back bogus search results. GNUnet
enables content providers to group related content and to establish a
reputation. Furthermore, GNUnet allows updates to certain content to be made
available. This section is supposed to introduce users to the concepts that are
used to achive these goals.


@menu
* Files::
* Keywords::
* Directories::
* Pseudonyms::
* Namespaces::
* Advertisements::
* Anonymity level::
* Content Priority::
* Replication::
@end menu

@node Files
@subsubsection Files
@c %**end of header

A file in GNUnet is just a sequence of bytes. Any file-format is allowed and the
maximum file size is theoretically 264 bytes, except that it would take an
impractical amount of time to share such a file. GNUnet itself never interprets
the contents of shared files, except when using GNU libextractor to obtain
keywords.

@node Keywords
@subsubsection Keywords
@c %**end of header

Keywords are the most simple mechanism to find files on GNUnet. Keywords are
@strong{case-sensitive} and the search string must always match @strong{exactly}
the keyword used by the person providing the file. Keywords are never
transmitted in plaintext. The only way for an adversary to determine the keyword
that you used to search is to guess it (which then allows the adversary to
produce the same search request). Since providing keywords by hand for each
shared file is tedious, GNUnet uses GNU libextractor to help automate this
process. Starting a keyword search on a slow machine can take a little while
since the keyword search involves computing a fresh RSA key to formulate the
request.

@node Directories
@subsubsection Directories
@c %**end of header

A directory in GNUnet is a list of file identifiers with meta data. The file
identifiers provide sufficient information about the files to allow downloading
the contents. Once a directory has been created, it cannot be changed since it
is treated just like an ordinary file by the network. Small files (of a few
kilobytes) can be inlined in the directory, so that a separate download becomes
unnecessary.

@node Pseudonyms
@subsubsection Pseudonyms
@c %**end of header

Pseudonyms in GNUnet are essentially public-private (RSA) key pairs that allow a
GNUnet user to maintain an identity (which may or may not be detached from his
real-life identity). GNUnet's pseudonyms are not file-sharing specific --- and
they will likely be used by many GNUnet applications where a user identity is
required.

Note that a pseudonym is NOT bound to a GNUnet peer. There can be multiple
pseudonyms for a single user, and users could (theoretically) share the private
pseudonym keys (currently only out-of-band by knowing which files to copy
around).

@node Namespaces
@subsubsection Namespaces
@c %**end of header

A namespace is a set of files that were signed by the same pseudonym. Files (or
directories) that have been signed and placed into a namespace can be updated.
Updates are identified as authentic if the same secret key was used to sign the
update. Namespaces are also useful to establish a reputation, since all of the
content in the namespace comes from the same entity (which does not have to be
the same person).

@node Advertisements
@subsubsection Advertisements
@c %**end of header

Advertisements are used to notify other users about the existence of a
namespace. Advertisements are propagated using the normal keyword search. When
an advertisement is received (in response to a search), the namespace is added
to the list of namespaces available in the namespace-search dialogs of
gnunet-fs-gtk and printed by gnunet-pseudonym. Whenever a namespace is created,
an appropriate advertisement can be generated. The default keyword for the
advertising of namespaces is "namespace".

Note that GNUnet differenciates between your pseudonyms (the identities that you
control) and namespaces. If you create a pseudonym, you will not automatically
see the respective namespace. You first have to create an advertisement for the
namespace and find it using keyword search --- even for your own namespaces. The
@code{gnunet-pseudonym} tool is currently responsible for both managing
pseudonyms and namespaces. This will likely change in the future to reduce the
potential for confusion.

@node Anonymity level
@subsubsection Anonymity level
@c %**end of header

The anonymity level determines how hard it should be for an adversary to
determine the identity of the publisher or the searcher/downloader. An
anonymity level of zero means that anonymity is not required. The default
anonymity level of "1" means that anonymous routing is desired, but no
particular amount of cover traffic is necessary. A powerful adversary might thus
still be able to deduce the origin of the traffic using traffic analysis.
Specifying higher anonymity levels increases the amount of cover traffic
required. While this offers better privacy, it can also significantly hurt
performance.

@node Content Priority
@subsubsection Content Priority
@c %**end of header

Depending on the peer's configuration, GNUnet peers migrate content between
peers. Content in this sense are individual blocks of a file, not necessarily
entire files. When peers run out of space (due to local publishing operations or
due to migration of content from other peers), blocks sometimes need to be
discarded. GNUnet first always discards expired blocks (typically, blocks are
published with an expiration of about two years in the future; this is another
option). If there is still not enough space, GNUnet discards the blocks with the
lowest priority. The priority of a block is decided by its popularity (in terms
of requests from peers we trust) and, in case of blocks published locally, the
base-priority that was specified by the user when the block was published
initially.

@node Replication
@subsubsection Replication
@c %**end of header

When peers migrate content to other systems, the replication level of a block is
used to decide which blocks need to be migrated most urgently. GNUnet will
always push the block with the highest replication level into the network, and
then decrement the replication level by one. If all blocks reach replication
level zero, the selection is simply random.

@node File-sharing Publishing
@subsection File-sharing Publishing
@c %**end of header

The command @code{gnunet-publish} can be used to add content to the network.
The basic format of the command is
@example
$ gnunet-publish [-n] [-k KEYWORDS]* [-m TYPE:VALUE] FILENAME
@end example


@menu
* Important command-line options::
* Indexing vs. Inserting::
@end menu

@node Important command-line options
@subsubsection Important command-line options
@c %**end of header

The option -k is used to specify keywords for the file that should be inserted.
You can supply any number of keywords, and each of the keywords will be
sufficient to locate and retrieve the file.

The -m option is used to specify meta-data, such as descriptions. You can use -m
multiple times. The TYPE passed must be from the list of meta-data types known
to libextractor. You can obtain this list by running @code{extract -L}.
Use quotes around the entire meta-data argument if the value contains spaces.
The meta-data is displayed to other users when they select which files to
download. The meta-data and the keywords are optional and maybe inferred using
@code{GNU libextractor}.

gnunet-publish has a few additional options to handle namespaces and
directories.
See the man-page for details.

@node Indexing vs. Inserting
@subsubsection Indexing vs Inserting
@c %**end of header

By default, GNUnet indexes a file instead of making a full copy. This is much
more efficient, but requries the file to stay unaltered at the location where it
was when it was indexed. If you intend to move, delete or alter a file, consider
using the option @code{-n} which will force GNUnet to make a copy of the file in
the database.

Since it is much less efficient, this is strongly discouraged for large files.
When GNUnet indexes a file (default), GNUnet does @strong{not} create an
additional encrypted copy of the file but just computes a summary (or index) of
the file. That summary is approximately two percent of the size of the original
file and is stored in GNUnet's database. Whenever a request for a part of an
indexed file reaches GNUnet, this part is encrypted on-demand and send out. This
way, there is no need for an additional encrypted copy of the file to stay
anywhere on the drive. This is different from other systems, such as Freenet,
where each file that is put online must be in Freenet's database in encrypted
format, doubling the space requirements if the user wants to preseve a directly
accessible copy in plaintext.

Thus indexing should be used for all files where the user will keep using this
file (at the location given to gnunet-publish) and does not want to retrieve it
back from GNUnet each time. If you want to remove a file that you have indexed
from the local peer, use the tool @code{gnunet-unindex} to un-index the file.

The option @code{-n} may be used if the user fears that the file might be found
on his drive (assuming the computer comes under the control of an adversary).
When used with the @code{-n} flag, the user has a much better chance of denying
knowledge of the existence of the file, even if it is still (encrypted) on the
drive and the adversary is able to crack the encryption (e.g. by guessing the
keyword.

@node File-sharing Searching
@subsection File-sharing Searching
@c %**end of header

The command @code{gnunet-search} can be used to search for content on GNUnet.
The format is:
@example
$ gnunet-search [-t TIMEOUT] KEYWORD
@end example

The -t option specifies that the query should timeout after approximately
TIMEOUT seconds. A value of zero is interpreted as @emph{no timeout}, which is
also the default. In this case, gnunet-search will never terminate (unless you
press CTRL-C).

If multiple words are passed as keywords, they will all be considered optional.
Prefix keywords with a "+" to make them mandatory.

Note that searching using
@example
$ gnunet-search Das Kapital
@end example

is not the same as searching for
@example
$ gnunet-search "Das Kapital"
@end example

as the first will match files shared under the keywords "Das" or "Kapital"
whereas the second will match files shared under the keyword "Das Kapital".

Search results are printed by gnunet-search like this:
@example
$ gnunet-download -o "COPYING" --- gnunet://fs/chk/N8...C92.17992
=> The GNU Public License <= (mimetype: text/plain)
@end example

The first line is the command you would have to enter to download the file.
The argument passed to @code{-o} is the suggested filename (you may change it to
whatever you like).
The @code{--} is followed by key for decrypting the file, the query for
searching the file, a checksum (in hexadecimal) finally the size of the file in
bytes.
The second line contains the description of the file; here this is
"The GNU Public License" and the mime-type (see the options for gnunet-publish
on how to specify these).

@node File-sharing Downloading
@subsection File-sharing Downloading
@c %**end of header

In order to download a file, you need the three values returned by
@code{gnunet-search}.
You can then use the tool @code{gnunet-download} to obtain the file:
@example
$ gnunet-download -o FILENAME --- GNUNETURL
@end example

FILENAME specifies the name of the file where GNUnet is supposed to write the
result. Existing files are overwritten. If the existing file contains blocks
that are identical to the desired download, those blocks will not be downloaded
again (automatic resume).

If you want to download the GPL from the previous example, you do the following:
@example
$ gnunet-download -o "COPYING" --- gnunet://fs/chk/N8...92.17992
@end example

If you ever have to abort a download, you can continue it at any time by
re-issuing @command{gnunet-download} with the same filename. In that case, GNUnet
will @strong{not} download blocks again that are already present.

GNUnet's file-encoding mechanism will ensure file integrity, even if the
existing file was not downloaded from GNUnet in the first place.

You may want to use the @command{-V} switch (must be added before the @command{--}) to
turn on verbose reporting. In this case, @command{gnunet-download} will print the
current number of bytes downloaded whenever new data was received.

@node File-sharing Directories
@subsection File-sharing Directories
@c %**end of header

Directories are shared just like ordinary files. If you download a directory
with @command{gnunet-download}, you can use @command{gnunet-directory} to list its
contents. The canonical extension for GNUnet directories when stored as files in
your local file-system is ".gnd". The contents of a directory are URIs and
meta data.
The URIs contain all the information required by @command{gnunet-download} to
retrieve the file. The meta data typically includes the mime-type, description,
a filename and other meta information, and possibly even the full original file
(if it was small).

@node File-sharing Namespace Management
@subsection File-sharing Namespace Management
@c %**end of header

THIS TEXT IS OUTDATED AND NEEDS TO BE REWRITTEN FOR 0.10!

The gnunet-pseudonym tool can be used to create pseudonyms and to advertise
namespaces. By default, gnunet-pseudonym simply lists all locally available
pseudonyms.


@menu
* Creating Pseudonyms::
* Deleting Pseudonyms::
* Advertising namespaces::
* Namespace names::
* Namespace root::
@end menu

@node Creating Pseudonyms
@subsubsection Creating Pseudonyms
@c %**end of header

With the @command{-C NICK} option it can also be used to create a new pseudonym.
A pseudonym is the virtual identity of the entity in control of a namespace.
Anyone can create any number of pseudonyms. Note that creating a pseudonym can
take a few minutes depending on the performance of the machine used.

@node Deleting Pseudonyms
@subsubsection Deleting Pseudonyms
@c %**end of header

With the @command{-D NICK} option pseudonyms can be deleted. Once the pseudonym has
been deleted it is impossible to add content to the corresponding namespace.
Deleting the pseudonym does not make the namespace or any content in it
unavailable.

@node Advertising namespaces
@subsubsection Advertising namespaces
@c %**end of header

Each namespace is associated with meta-data that describes the namespace.
This meta data is provided by the user at the time that the namespace is
advertised. Advertisements are published under keywords so that they can be
found using normal keyword-searches. This way, users can learn about new
namespaces without relying on out-of-band communication or directories.
A suggested keyword to use for all namespaces is simply "namespace".
When a keyword-search finds a namespace advertisement, it is automatically
stored in a local list of known namespaces. Users can then associate a rank with
the namespace to remember the quality of the content found in it.

@node Namespace names
@subsubsection Namespace names
@c %**end of header

While the namespace is uniquely identified by its ID, another way to refer to
the namespace is to use the NICKNAME. The NICKNAME can be freely chosen by the
creator of the namespace and hence conflicts are possible. If a GNUnet client
learns about more than one namespace using the same NICKNAME, the ID is appended
to the NICKNAME to get a unique identifier.

@node Namespace root
@subsubsection Namespace root
@c %**end of header

An item of particular interest in the namespace advertisement is the ROOT.
The ROOT is the identifier of a designated entry in the namespace. The idea is
that the ROOT can be used to advertise an entry point to the content of the
namespace.

@node File-Sharing URIs
@subsection File-Sharing URIs
@c %**end of header

GNUnet (currently) uses four different types of URIs for file-sharing. They all
begin with "gnunet://fs/". This section describes the four different URI types
in detail.


@menu
* Encoding of hash values in URIs::
* Content Hash Key (chk)::
* Location identifiers (loc)::
* Keyword queries (ksk)::
* Namespace content (sks)::
@end menu

@node Encoding of hash values in URIs
@subsubsection Encoding of hash values in URIs
@c %**end of header

Most URIs include some hash values. Hashes are encoded using base32hex
(RFC 2938).

@node Content Hash Key (chk)
@subsubsection Content Hash Key (chk)
@c %**end of header

A chk-URI is used to (uniquely) identify a file or directory and to allow peers
to download the file. Files are stored in GNUnet as a tree of encrypted blocks.
The chk-URI thus contains the information to download and decrypt those blocks.
A chk-URI has the format "gnunet://fs/chk/KEYHASH.QUERYHASH.SIZE". Here, "SIZE"
is the size of the file (which allows a peer to determine the shape of the
tree), KEYHASH is the key used to decrypt the file (also the hash of the
plaintext of the top block) and QUERYHASH is the query used to request the
top-level block (also the hash of the encrypted block).

@node Location identifiers (loc)
@subsubsection Location identifiers (loc)
@c %**end of header

For non-anonymous file-sharing, loc-URIs are used to specify which peer is
offering the data (in addition to specifying all of the data from a chk-URI).
Location identifiers include a digital signature of the peer to affirm that the
peer is truly the origin of the data. The format is
"gnunet://fs/loc/KEYHASH.QUERYHASH.SIZE.PEER.SIG.EXPTIME". Here, "PEER" is the
public key of the peer (in GNUnet format in base32hex), SIG is the RSA signature
(in GNUnet format in base32hex) and EXPTIME specifies when the signature expires
(in milliseconds after 1970).

@node Keyword queries (ksk)
@subsubsection Keyword queries (ksk)
@c %**end of header

A keyword-URI is used to specify that the desired operation is the search using
a particular keyword. The format is simply "gnunet://fs/ksk/KEYWORD". Non-ASCII
characters can be specified using the typical URI-encoding (using hex values)
from HTTP. "+" can be used to specify multiple keywords (which are then
logically "OR"-ed in the search, results matching both keywords are given a
higher rank): "gnunet://fs/ksk/KEYWORD1+KEYWORD2".

@node Namespace content (sks)
@subsubsection Namespace content (sks)
@c %**end of header

Namespaces are sets of files that have been approved by some (usually
pseudonymous) user --- typically by that user publishing all of the files
together. A file can be in many namespaces. A file is in a namespace if the
owner of the ego (aka the namespace's private key) signs the CHK of the file
cryptographically. An SKS-URI is used to search a namespace. The result is a
block containing meta data, the CHK and the namespace owner's signature. The
format of a sks-URI is "gnunet://fs/sks/NAMESPACE/IDENTIFIER". Here, "NAMESPACE"
is the public key for the namespace. "IDENTIFIER" is a freely chosen keyword
(or password!). A commonly used identifier is "root" which by convention refers
to some kind of index or other entry point into the namespace.

@node The GNU Name System
@section The GNU Name System
@c %**end of header


The GNU Name System (GNS) is secure and decentralized naming system.
It allows its users to resolve and register names within the @code{.gnu}
@dfn{top-level domain} (TLD).

GNS is designed to provide:
@itemize @bullet
@item Censorship resistance
@item Query privacy
@item Secure name resolution
@item Compatibility with DNS
@end itemize

For the initial configuration and population of your GNS installation, please
follow the GNS setup instructions. The remainder of this chapter will provide
some background on GNS and then describe how to use GNS in more detail.

Unlike DNS, GNS does not rely on central root zones or authorities. Instead any
user administers his own root and can can create arbitrary name value mappings.
Furthermore users can delegate resolution to other users' zones just like DNS NS
records do. Zones are uniquely identified via public keys and resource records
are signed using the corresponding public key. Delegation to another user's zone
is done using special PKEY records and petnames. A petname is a name that can be
freely chosen by the user. This results in non-unique name-value mappings as
@code{@uref{http://www.bob.gnu/, www.bob.gnu}} to one user might be
@code{@uref{http://www.friend.gnu/, www.friend.gnu}} for someone else.


@menu
* Maintaining your own Zones::
* Obtaining your Zone Key::
* Adding Links to Other Zones::
* The Three Local Zones of GNS::
* The Master Zone::
* The Private Zone::
* The Shorten Zone::
* The ZKEY Top Level Domain in GNS::
* Resource Records in GNS::
@end menu


@node Maintaining your own Zones
@subsection Maintaining your own Zones

To setup your GNS system you must execute:

@example
$ gnunet-gns-import.sh
@end example

This will boostrap your zones and create the necessary key material.
Your keys can be listed using the gnunet-identity command line tool:

@example
$ gnunet-identity -d
@end example

You can arbitrarily create your own zones using the gnunet-identity tool using:

@example
$ gnunet-identity -C "new_zone"
@end example

Now you can add (or edit, or remove) records in your GNS zone using the
gnunet-setup GUI or using the gnunet-namestore command-line tool. In either
case, your records will be stored in an SQL database under control of the
gnunet-service-namestore. Note that if mutliple users use one peer, the
namestore database will include the combined records of all users. However,
users will not be able to see each other's records if they are marked as
private.

To provide a simple example for editing your own zone, suppose you have your own
web server with IP 1.2.3.4. Then you can put an A record (A records in DNS are
for IPv4 IP addresses) into your local zone using the command:@

@example
$ gnunet-namestore -z master-zone -a -n www -t A -V 1.2.3.4 -e never
@end example

Afterwards, you will be able to access your webpage under "www.gnu" (assuming
your webserver does not use virtual hosting, if it does, please read up on
setting up the GNS proxy).

Similar commands will work for other types of DNS and GNS records, the syntax
largely depending on the type of the record. Naturally, most users may find
editing the zones using the gnunet-setup GUI to be easier.

@node Obtaining your Zone Key
@subsection Obtaining your Zone Key

Each zone in GNS has a public-private key. Usually, gnunet-namestore and
gnunet-setup will access your private key as necessary, so you do not have to
worry about those. What is important is your public key (or rather, the hash of
your public key), as you will likely want to give it to others so that they can
securely link to you.

You can usually get the hash of your public key using@

@example
$ gnunet-identity -d $options | grep master-zone | awk '@{print $3@}'
@end example

For example, the output might be something like:

@example
DC3SEECJORPHQNVRH965A6N74B1M37S721IG4RBQ15PJLLPJKUE0
@end example

Alternatively, you can obtain a QR code with your zone key AND your pseudonym
from gnunet-gtk. The QR code is displayed in the GNS tab and can be stored to
disk using the Save as button next to the image.

@node Adding Links to Other Zones
@subsection Adding Links to Other Zones


A central operation in GNS is the ability to securely delegate to other zones.
Basically, by adding a delegation you make all of the names from the other zone
available to yourself. This section describes how to create delegations.

Suppose you have a friend who you call 'bob' who also uses GNS. You can then
delegate resolution of names to Bob's zone by adding a PKEY record to his local
zone:

@example
$ gnunet-namestore -a -n bob --type PKEY -V XXXX -e never
@end example

Note that XXXX in the command above must be replaced with the hash of Bob's
public key (the output your friend obtained using the gnunet-identity command
from the previous section and told you, for example by giving you a business
card containing this information as a QR code).

Assuming Bob has an A record for his website under the name of www in his zone,
you can then access Bob's website under www.bob.gnu --- as well as any (public)
GNS record that Bob has in his zone by replacing www with the respective name of
the record in Bob's zone.

Furthermore, if Bob has himself a (public) delegation to Carol's zone under
"carol", you can access Carol's records under NAME.carol.bob.gnu (where NAME is
the name of Carol's record you want to access).

@node The Three Local Zones of GNS
@subsection The Three Local Zones of GNS

Each user GNS has control over three zones. Each of the zones has a different
purpose. These zones are the
@itemize @bullet

@item master zone,
@item private zone, and the
@item shorten zone.
@end itemize

@node The Master Zone
@subsection The Master Zone


The master zone is your personal TLD. Names within the @code{.gnu} namespace are
resolved relative to this zone. You can arbitrarily add records to this zone and
selectively publish those records.

@node The Private Zone
@subsection The Private Zone


The private zone is a subzone (or subdomain in DNS terms) of your master zone.
It should be used for records that you want to keep private. For example
@code{bank.private.gnu}. The key idea is that you want to keep your private
records separate, if just to know that those names are not available to other
users.

@node The Shorten Zone
@subsection The Shorten Zone


The shorten zone can either be a subzone of the master zone or the private zone.
It is different from the other zones in that GNS will automatically populate
this zone with other users' zones based on their PSEU records whenever you
resolve a name.

For example if you go to
@code{@uref{http://www.bob.alice.dave.gnu/, www.bob.alice.dave.gnu}}, GNS will
try to import @code{bob} into your shorten zone. Having obtained Bob's PKEY from
@code{alice.dave.gnu}, GNS will lookup the PSEU record for @code{+} in Bob's
zone. If it exists and the specified pseudonym is not taken, Bob's PKEY will be
automatically added under that pseudonym (i.e. "bob") into your shorten zone.
From then on, Bob's webpage will also be available for you as
@code{@uref{http://www.bob.short.gnu/, www.bob.short.gnu}}. This feature is
called automatic name shortening and is supposed to keep GNS names as short and
memorable as possible.

@node The ZKEY Top Level Domain in GNS
@subsection The ZKEY Top Level Domain in GNS


GNS also provides a secure and globally unique namespace under the .zkey
top-level domain. A name in the .zkey TLD corresponds to the (printable) public
key of a zone. Names in the .zkey TLD are then resolved by querying the
respective zone. The .zkey TLD is expected to be used under rare circumstances
where globally unique names are required and for integration with legacy
systems.

@node Resource Records in GNS
@subsection Resource Records in GNS


GNS supports the majority of the DNS records as defined in
@uref{http://www.ietf.org/rfc/rfc1035.txt, RFC 1035}. Additionally, GNS defines
some new record types the are unique to the GNS system. For example,
GNS-specific resource records are use to give petnames for zone delegation,
revoke zone keys and provide some compatibility features.

For some DNS records, GNS does extended processing to increase their usefulness
in GNS. In particular, GNS introduces special names referred to as
"zone relative names". Zone relative names are allowed in some resource record
types (for example, in NS and CNAME records) and can also be used in links on
webpages. Zone relative names end in ".+" which indicates that the name needs to
be resolved relative to the current authoritative zone. The extended processing
of those names will expand the ".+" with the correct delegation chain to the
authoritative zone (replacing ".+" with the name of the location where the name
was encountered) and hence generate a valid @code{.gnu} name.

GNS currently supports the following record types:

@menu
* NICK::
* PKEY::
* BOX::
* LEHO::
* VPN::
* A AAAA and TXT::
* CNAME::
* GNS2DNS::
* SOA SRV PTR and MX::
@end menu

@node NICK
@subsubsection NICK

A NICK record is used to give a zone a name. With a NICK record, you can
essentially specify how you would like to be called. GNS expects this record
under the name "+" in the zone's database (NAMESTORE); however, it will then
automatically be copied into each record set, so that clients never need to do a
separate lookup to discover the NICK record.

@b{Example}@

@example
Name: +; RRType: NICK; Value: bob
@end example

This record in Bob's zone will tell other users that this zone wants to be
referred to as 'bob'. Note that nobody is obliged to call Bob's zone 'bob' in
their own zones. It can be seen as a recommendation ("Please call me 'bob'").

@node PKEY
@subsubsection PKEY

PKEY records are used to add delegation to other users' zones and give those
zones a petname.

@b{Example}@

Let Bob's zone be identified by the hash "ABC012". Bob is your friend so you
want to give him the petname "friend". Then you add the following record to your
zone:

@example
Name: friend; RRType: PKEY; Value: ABC012;
@end example

This will allow you to resolve records in bob's zone under "*.friend.gnu".

@node BOX
@subsubsection BOX

BOX records are there to integrate information from TLSA or SRV records under
the main label. In DNS, TLSA and SRV records use special names of the form
@code{_port._proto.(label.)*tld} to indicate the port number and protocol
(i.e. tcp or udp) for which the TLSA or SRV record is valid. This causes various
problems, and is elegantly solved in GNS by integrating the protocol and port
numbers together with the respective value into a "BOX" record. Note that in the
GUI, you do not get to edit BOX records directly right now --- the GUI will
provide the illusion of directly editing the TLSA and SRV records, even though
they internally are BOXed up.

@node LEHO
@subsubsection LEHO

The LEgacy HOstname of a server. Some webservers expect a specific hostname to
provide a service (virtiual hosting). Also SSL certificates usually contain DNS
names. To provide the expected legacy DNS name for a server, the LEHO record can
be used. To mitigate the just mentioned issues the GNS proxy has to be used. The
GNS proxy will use the LEHO information to apply the necessary transformations.

@node VPN
@subsubsection VPN

GNS allows easy access to services provided by the GNUnet Virtual Public
Network. When the GNS resolver encounters a VPN record it will contact the VPN
service to try and allocate an IPv4/v6 address (if the queries record type is an
IP address) that can be used to contact the service.

@b{Example}@

I want to provide access to the VPN service "web.gnu." on port 80 on peer
ABC012:@
Name: www; RRType: VPN; Value: 80 ABC012 web.gnu.

The peer ABC012 is configured to provide an exit point for the service
"web.gnu." on port 80 to it's server running locally on port 8080 by having the
following lines in the @file{gnunet.conf} configuration file:@
@example
[web.gnunet.]
TCP_REDIRECTS = 80:localhost4:8080
@end example

@node A AAAA and TXT
@subsubsection A AAAA and TXT

Those records work in exactly the same fashion as in traditional DNS.

@node CNAME
@subsubsection CNAME

As specified in RFC 1035 whenever a CNAME is encountered the query needs to be
restarted with the specified name. In GNS a CNAME can either be:

@itemize @bullet
@item A zone relative name,
@item A zkey name or
@item A DNS name (in which case resolution will continue outside of GNS with the systems DNS resolver)
@end itemize

@node GNS2DNS
@subsubsection GNS2DNS

GNS can delegate authority to a legacy DNS zone. For this, the name of the DNS
nameserver and the name of the DNS zone are specified in a GNS2DNS record.

@b{Example}

@example
Name: pet; RRType: GNS2DNS; Value: gnunet.org@@a.ns.joker.com
@end example

Any query to @code{pet.gnu} will then be delegated to the DNS server at
@code{a.ns.joker.com}.@
For example, @code{@uref{http://www.pet.gnu/, www.pet.gnu}} will result in a
DNS query for @code{@uref{http://www.gnunet.org/, www.gnunet.org}} to the server
at @code{a.ns.joker.com}. Delegation to DNS via NS records in GNS can be useful
if you do not want to start resolution in the DNS root zone (due to issues such
as censorship or availability).

Note that you would typically want to use a relative name for the nameserver,
i.e.
@example
Name: pet; RRType: GNS2DNS; Value: gnunet.org@@ns-joker.+@
Name: ns-joker; RRType: A; Value: 184.172.157.218
@end example

This way, you can avoid involving the DNS hierarchy in the resolution of
@code{a.ns.joker.com}. In the example above, the problem may not be obvious as
the nameserver for "gnunet.org" is in the ".com" zone. However, imagine the
nameserver was "ns.gnunet.org". In this case, delegating to "ns.gnunet.org"
would mean that despite using GNS, censorship in the DNS ".org" zone would still
be effective.

@node SOA SRV PTR and MX
@subsubsection SOA SRV PTR and MX

The domain names in those records can, again, be either
@itemize @bullet
@item A zone relative name,
@item A zkey name or
@item A DNS name
@end itemize

The resolver will expand the zone relative name if possible. Note that when
using MX records within GNS, the target mail server might still refuse to accept
e-mails to the resulting domain as the name might not match. GNS-enabled mail
clients should use the ZKEY zone as the destination hostname and GNS-enabled
mail servers should be configured to accept e-mails to the ZKEY-zones of all
local users.

@node Using the Virtual Public Network
@section Using the Virtual Public Network

@menu
* Setting up an Exit node::
* Fedora and the Firewall::
* Setting up VPN node for protocol translation and tunneling::
@end menu

Using the GNUnet Virtual Public Network (VPN) application you can tunnel IP
traffic over GNUnet. Moreover, the VPN comes with built-in protocol translation
and DNS-ALG support, enabling IPv4-to-IPv6 protocol translation
(in both directions). This chapter documents how to use the GNUnet VPN.

The first thing to note about the GNUnet VPN is that it is a public network. All
participating peers can participate and there is no secret key to control
access. So unlike common virtual private networks, the GNUnet VPN is not useful
as a means to provide a "private" network abstraction over the Internet. The
GNUnet VPN is a virtual network in the sense that it is an overlay over the
Internet, using its own routing mechanisms and can also use an internal
addressing scheme. The GNUnet VPN is an Internet underlay --- TCP/IP
applications run on top of it.

The VPN is currently only supported on GNU/Linux systems. Support for operating
systems that support TUN (such as FreeBSD) should be easy to add (or might not
even require any coding at all --- we just did not test this so far). Support
for other operating systems would require re-writing the code to create virtual
network interfaces and to intercept DNS requests.

The VPN does not provide good anonymity. While requests are routed over the
GNUnet network, other peers can directly see the source and destination of each
(encapsulated) IP packet. Finally, if you use the VPN to access Internet
services, the peer sending the request to the Internet will be able to observe
and even alter the IP traffic. We will discuss additional security implications
of using the VPN later in this chapter.

@node Setting up an Exit node
@subsection Setting up an Exit node

Any useful operation with the VPN requires the existence of an exit node in the
GNUnet Peer-to-Peer network. Exit functionality can only be enabled on peers
that have regular Internet access. If you want to play around with the VPN or
support the network, we encourage you to setup exit nodes. This chapter
documents how to setup an exit node.

There are four types of exit functions an exit node can provide, and using the
GNUnet VPN to access the Internet will only work nicely if the first three types
are provided somewhere in the network. The four exit functions are:
@itemize @bullet
@item DNS: allow other peers to use your DNS resolver
@item IPv4: allow other peers to access your IPv4 Internet connection
@item IPv6: allow other peers to access your IPv6 Internet connection
@item Local service: allow other peers to access a specific TCP or UDP service your peer is providing
@end itemize

By enabling "exit" in gnunet-setup and checking the respective boxes in the
"exit" tab, you can easily choose which of the above exit functions you want to
support.

Note, however, that by supporting the first three functions you will allow
arbitrary other GNUnet users to access the Internet via your system. This is
somewhat similar to running a Tor exit node. The torproject has a nice article
about what to consider if you want to do this here. We believe that generally
running a DNS exit node is completely harmless.

The exit node configuration does currently not allow you to restrict the
Internet traffic that leaves your system. In particular, you cannot exclude SMTP
traffic (or block port 25) or limit to HTTP traffic using the GNUnet
configuration. However, you can use your host firewall to restrict outbound
connections from the virtual tunnel interface. This is highly recommended. In
the future, we plan to offer a wider range of configuration options for exit
nodes.

Note that by running an exit node GNUnet will configure your kernel to perform
IP-forwarding (for IPv6) and NAT (for IPv4) so that the traffic from the virtual
interface can be routed to the Internet. In order to provide an IPv6-exit, you
need to have a subnet routed to your host's external network interface and
assign a subrange of that subnet to the GNUnet exit's TUN interface.

When running a local service, you should make sure that the local service is
(also) bound to the IP address of your EXIT interface (i.e. 169.254.86.1). It
will NOT work if your local service is just bound to loopback. You may also want
to create a "VPN" record in your zone of the GNU Name System to make it easy for
others to access your service via a name instead of just the full service
descriptor. Note that the identifier you assign the service can serve as a
passphrase or shared secret, clients connecting to the service must somehow
learn the service's name. VPN records in the GNU Name System can make this
easier.

@node Fedora and the Firewall
@subsection Fedora and the Firewall


When using an exit node on Fedora 15, the standard firewall can create trouble
even when not really exiting the local system! For IPv4, the standard rules seem
fine. However, for IPv6 the standard rules prohibit traffic from the network
range of the virtual interface created by the exit daemon to the local IPv6
address of the same interface (which is essentially loopback traffic, so you
might suspect that a standard firewall would leave this traffic alone). However,
as somehow for IPv6 the traffic is not recognized as originating from the local
system (and as the connection is not already "established"), the firewall drops
the traffic. You should still get ICMPv6 packets back, but that's obviously not
very useful.

Possible ways to fix this include disabling the firewall (do you have a good
reason for having it on?) or disabling the firewall at least for the GNUnet exit
interface (or the respective IPv4/IPv6 address range). The best way to diagnose
these kinds of problems in general involves setting the firewall to REJECT
instead of DROP and to watch the traffic using wireshark (or tcpdump) to see if
ICMP messages are generated when running some tests that should work.

@node Setting up VPN node for protocol translation and tunneling
@subsection Setting up VPN node for protocol translation and tunneling


The GNUnet VPN/PT subsystem enables you to tunnel IP traffic over the VPN to an
exit node, from where it can then be forwarded to the Internet. This section
documents how to setup VPN/PT on a node. Note that you can enable both the VPN
and an exit on the same peer. In this case, IP traffic from your system may
enter your peer's VPN and leave your peer's exit. This can be useful as a means
to do protocol translation. For example, you might have an application that
supports only IPv4 but needs to access an IPv6-only site. In this case, GNUnet
would perform 4to6 protocol translation between the VPN (IPv4) and the
Exit (IPv6). Similarly, 6to4 protocol translation is also possible. However, the
primary use for GNUnet would be to access an Internet service running with an
IP version that is not supported by your ISP. In this case, your IP traffic
would be routed via GNUnet to a peer that has access to the Internet with the
desired IP version.

Setting up an entry node into the GNUnet VPN primarily requires you to enable
the "VPN/PT" option in "gnunet-setup". This will launch the
"gnunet-service-vpn", "gnunet-service-dns" and "gnunet-daemon-pt" processes.
The "gnunet-service-vpn" will create a virtual interface which will be used as
the target for your IP traffic that enters the VPN. Additionally, a second
virtual interface will be created by the "gnunet-service-dns" for your DNS
traffic. You will then need to specify which traffic you want to tunnel over
GNUnet. If your ISP only provides you with IPv4 or IPv6-access, you may choose
to tunnel the other IP protocol over the GNUnet VPN. If you do not have an ISP
(and are connected to other GNUnet peers via WLAN), you can also choose to
tunnel all IP traffic over GNUnet. This might also provide you with some
anonymity. After you enable the respective options and restart your peer, your
Internet traffic should be tunneled over the GNUnet VPN.

The GNUnet VPN uses DNS-ALG to hijack your IP traffic. Whenever an application
resolves a hostname (i.e. 'gnunet.org'), the "gnunet-daemon-pt" will instruct
the "gnunet-service-dns" to intercept the request (possibly route it over GNUnet
as well) and replace the normal answer with an IP in the range of the VPN's
interface. "gnunet-daemon-pt" will then tell "gnunet-service-vpn" to forward all
traffic it receives on the TUN interface via the VPN to the original
destination.

For applications that do not use DNS, you can also manually create such a
mapping using the gnunet-vpn command-line tool. Here, you specfiy the desired
address family of the result (i.e. "-4"), and the intended target IP on the
Internet ("-i 131.159.74.67") and "gnunet-vpn" will tell you which IP address in
the range of your VPN tunnel was mapped.

gnunet-vpn can also be used to access "internal" services offered by GNUnet
nodes. So if you happen to know a peer and a service offered by that peer, you
can create an IP tunnel to that peer by specifying the peer's identity, service
name and protocol (--tcp or --udp) and you will again receive an IP address that
will terminate at the respective peer's service.
